关键词: 转杯纺, 弯钩纤维, 纤维伸直度, 纤维形态变化, 数值模拟

Abstract: Rotor spinning is a widely used new spinning method with the advantages of short process flow and high production efficiency. The fiber strands are directly fed into the carding device and released into a single fiber state, and are transferred to the rotor through negative pressure airflow for condensation and twisting into yarn. The fibers fed into the rotor spinning machine contain various forms of fibers, and are mainly divided into the three categories of straight fibers, front hook fibers, and rear hook fibers. In actual production, it is necessary to avoid the entry of rear hook fibers. If there are many rear hook fibers, the spun rotor yarn may have uneven evenness and easily produce coarse and fine knots. This is the experience summarized in the production process. Therefore, exploring the morphological changes of hook fibers in the rotor spinning machine, as well as the straightening and formation process of hooks, provides reference for improving the spinning mechanism of rotor spinning, and optimizing the rotor structure and process parameters.
We aimed to solve the fiber motion trajectory using the Lagrangian-Euler method, with the airflow as a continuous phase and the fibers as discrete phases. Firstly, we used the 3D modeling software SolidWorks2021 to establish a model of the rotor spinning machine. Then, we coupled and connected Rocky DEM 2022R1 and ANSYS Fluent 2022R1. As for the airflow field, we selected the Standard k-epsilon turbulence model, Standard Wall Function (SWF), and SIMPLE algorithm. The fiber model is of a rod chain structure, and is made of cotton fibers with a length of 28mm. The fiber model established in this article has the size and properties of real cotton fibers, and has been optimized on the fiber model. At the same time, the changes in fiber morphology under different initial forms were considered. The deformation pattern of the hook fibers in the fiber transmission channel under conditions 1-2 is basically consistent, with a small trend of movement towards the main section in the bent section; from the exit of the fiber transport channel to the slip surface, different hooked fibers undergo different morphological differentiation processes; the pattern of morphological changes in the coagulation tank is also roughly the same, with the fibers transitioning from wavy bending to a state close to the inside of the coagulation tank. When the front hook fiber completely enters the condensation groove, the hook part has been straightened and eliminated; after the non-straightened rear hook fibers in the fiber transmission channel enter the condensation tank, it is difficult to fully straighten the hook part. The straightness of the front hook fibers in the condensation groove is significantly higher than that of the rear hook fibers. Therefore, feeding fibers into the rotor spinning machine in the form of hooks can optimize the yarn structure. 
To sum up, numerical simulation is a very good research method. Firstly, computer simulation of the flow field and fiber movement process inside the rotor spinning machine can provide theoretical guidance for production optimization and design solutions, reduce experimental trial and error costs, and improve efficiency. Secondly, by conducting in-depth research on the airflow field and fiber movement process inside the spinner, the mechanism of rotor spinning yarn formation is gradually improved, providing a theoretical basis for the key components such as the fiber conveying channel and rotor in rotor spinning.

Key words: rotor spinning, hook fibers, fiber straightness, changes in fiber morphology, numerical simulation